Postnatal development of the rat portal vein: correlation with occurrence of peptidergic innervation

Positive psychological effects of seated acupressure massage are associated with a rise in plasma oxytocin without affecting CGRP levels or circulating IL-6

Work-related stress is a major public health issue. Given the relationship between acute stress responses and health, finding strategies to deal with the unpleasant symptoms brought on by stress is essential. Massage therapy is a popular stress-reduction technique, but its effectiveness has yet to be shown. In that matter, this study investigates the effects of a 17-minute session of seated Amma massage on young healthy people. Subjective stress perception, anxiety and self-confidence were assessed before and after the massage using the Spielberger State Anxiety Scale (STAI-Y, Spielberger et al., 1983) and the Competitive State Anxiety Inventory (EEAC, Cury et al., 1999), together with cardiovascular parameters. Cortisol, CGRP, IL-6, and oxytocin plasma levels were measured before and after the massage to investigate its possible mode of action. This study enrolled 59 people: 33 receiving the massage, and 26 controls only seated on the massage chair. Interaction Time x Group demonstrates significant differences for all psychological measurements (STAI, EEAC) before and after the Amma massage, showing a beneficial effect of this treatment, in particular on perceived anxiety and self-confidence. No evidence was found of any correlation between cortisol plasma levels and psychological outcomes. No relationship was shown between the decrease of perceived stress and measured CGRP or IL-6 release, but the data demonstrated that heart frequency could be slightly decreased. The oxytocin plasma levels were significantly increased by the massage and could be responsible for the recovery of psychological outcomes. We conclude that seated acupressure Amma massage could be a useful tool to ameliorate quality of life at work.

Hepatic nervous system and neurobiology of the liver

The liver has a nervous system containing both afferent and efferent neurons that are involved in a number of processes. The afferent arm includes the sensation of lipids, glucose, and metabolites (after eating and drinking) and triggers the nervous system to make appropriate physiological changes. The efferent arm is essential for metabolic regulation, modulation of fibrosis and biliary function and the control of a number of other processes. Experimental models have helped us to establish how: (i) the liver is innervated by the autonomic nervous system; and (ii) the cell types that are involved in these processes. Thus, the liver acts as both a sensor and effector that is influenced by neurological signals and ablation. Understanding these processes hold significant implications in disease processes such as diabetes and obesity, which are influenced by appetite and hormonal signals.

Structural organization of hepatic portal vein in rat with special reference to musculature, intimal folds, and endothelial cell alignment

Structural organization of hepatic portal vein (HPV) was examined in adult rats by means of light and electron microscopy. Three characteristic features were found in the wall structure of rat HPV. (1) Tunica media consisted of two kinds of smooth muscle. The inner circular smooth muscle (CSM) was composed with one or two layer of smooth muscle cells, and was found in the entire length of the HPV and its tributaries. The outer longitudinal smooth muscle (LSM) was limited to a specific region of HPV; in particular it was well-developed at distal half of HPV. CSM counteracts luminal hydrostatic pressure to prevent circumferential hyperextension of venous wall, whereas LSM is likely to counteract a tractive force produced by gravity and movement of small intestine. (2) Intima of HPV showed a unique feature, intimal folds, which protruded into the lumen and were aligned almost circumferentially. Intimal folds were found only at the same region where the LSM was well-developed. Thus, LSM is presumably involved in the formation of intimal folds. (3) The endothelial cells between intimal folds were circumferentially aligned along the folds, although those in the other regions of HPV were arrayed along the longitudinal axis of HPV or the direction of blood flow as reported in other kinds of blood vessel. This finding implied that the circumferential blood flow locally occurs on the surface of intima between the intimal folds.

Vascular smooth muscle phenotypic diversity and function

The control of force production in vascular smooth muscle is critical to the normal regulation of blood flow and pressure, and altered regulation is common to diseases such as hypertension, heart failure, and ischemia. A great deal has been learned about imbalances in vasoconstrictor and vasodilator signals, e.g., angiotensin, endothelin, norepinephrine, and nitric oxide, that regulate vascular tone in normal and disease contexts. In contrast there has been limited study of how the phenotypic state of the vascular smooth muscle cell may influence the contractile response to these signaling pathways dependent upon the developmental, tissue-specific (vascular bed) or disease context. Smooth, skeletal, and cardiac muscle lineages are traditionally classified into fast or slow sublineages based on rates of contraction and relaxation, recognizing that this simple dichotomy vastly underrepresents muscle phenotypic diversity. A great deal has been learned about developmental specification of the striated muscle sublineages and their phenotypic interconversions in the mature animal under the control of mechanical load, neural input, and hormones. In contrast there has been relatively limited study of smooth muscle contractile phenotypic diversity. This is surprising given the number of diseases in which smooth muscle contractile dysfunction plays a key role. This review focuses on smooth muscle contractile phenotypic diversity in the vascular system, how it is generated, and how it may determine vascular function in developmental and disease contexts.

The role of the autonomic nervous liver innervation in the control of energy metabolism

Despite a longstanding research interest ever since the early work by Claude Bernard, the functional significance of autonomic liver innervation, either sympathetic or parasympathetic, is still ill defined. This scarcity of information not only holds for the brain control of hepatic metabolism, but also for the metabolic sensing function of the liver and the way in which this metabolic information from the liver affects the brain. Clinical information from the bedside suggests that successful human liver transplantation (implying a complete autonomic liver denervation) causes no life threatening metabolic derangements, at least in the absence of severe metabolic challenges such as hypoglycemia. However, from the benchside, data are accumulating that interference with the neuronal brain-liver connection does cause pronounced changes in liver metabolism. This review provides an extensive overview on how metabolic information is sensed by the liver, and how this information is processed via neuronal pathways to the brain. With this information the brain controls liver metabolism and that of other organs and tissues. We will pay special attention to the hypothalamic pathways involved in these liver-brain-liver circuits. At this stage, we still do not know the final destination and processing of the metabolic information that is transferred from the liver to the brain. On the other hand, in recent years, there has been a considerable increase in the understanding which brain areas are involved in the control of liver metabolism via its autonomic innervation. However, in view of the ever rising prevalence of type 2 diabetes, this potentially highly relevant knowledge is still by far too limited. Thus the autonomic innervation of the liver and its role in the control of metabolism needs our continued and devoted attention.

Potential role of the neuropeptide CGRP in the induction of differentiation of rat hepatic portal vein wall

The media of the rat hepatic portal vein is composed of an internal circular muscular layer (CL) and an external longitudinal muscular layer (LL). These two perpendicular layers differentiate progressively from mesenchymal cells within the first month after birth. In this paper, we studied the development of calcitonin gene-related peptide (CGRP) innervation during post-natal differentiation of the vessel. We show that CGRP innervation is already present around the vessel at birth in the future adventitia but far from the lumen of the vessel. Progressively, CGRP immunoreactive fibers reached first LL then CL. CL by itself become only innervated at day 14 after birth. This corresponds to the time at which thick filaments (myosin) are visible in electron microscopy and desmin visualisable by immunocytochemistry. Furthermore, we provide evidence by autoradiography, that binding sites for CGRP are transiently expressed on the portal vein media at day 1 and 14 after birth. Vascular smooth muscle cells were transfected with constructs containing promoters for desmin or smooth muscle myosin heavy chain (smMHC). CGRP treatment of the cells significantly increased the expression of smMHC. Overall these results suggest that CGRP can potentially influence the differentiation of smooth muscle cells from the vessel wall.

The neuropeptide calcitonin gene-related peptide differently modulates proliferation and differentiation of smooth muscle cells in culture depending on the cell type

Calcitonin gene-related peptide (CGRP) is a neuropeptide present around vasculature very early during development, when smooth muscle cells (SMC) are still proliferating and not yet totally differentiated. We investigated the effects of CGRP on proliferation and differentiation of SMC in culture; 10(-7) M CGRP added in the medium of cultured smooth muscle cells every 2 days did not significantly changed cells growth rate in 1% FCS. At the opposite, this treatment modulated proliferation of cells grown in 10% FCS medium. Two distinct populations of SMC with different growth rates were obtained from our primary cultures. SMC which proliferated slowly in the presence of 10% fetal calf serum (FCS) had growth rates positively influenced by CGRP. The quantity of alpha-smooth actin expressed by these cells was not influenced by the peptide. On the contrary, SMC which proliferated more rapidly in 10% FCS medium had growth rate inhibited by CGRP. In these cells, CGRP significantly reduced the amount of expressed alpha-smooth actin, an index of SMC differentiation. In both cases, the peptide significantly increased the level of mRNA for all the actin genes. In the light of this dual role of CGRP, it can be presumed that this peptide controls smooth muscle cells proliferation and differentiation in vivo and could thus regulate the homeostasis of the vessel wall.

Vasoactive intestinal polypeptide and calcitonin gene-related peptide in the developing rat heart atria

Vasoactive intestinal polypeptide-like immunoreactivity (VIP-LI) and calcitonin gene-related peptide (CGRP)-LI concentrations were determined in the developing rat heart atria using radioimmunoassay. Peptide levels were analysed on postnatal days 1, 10, 25, 45, 60, and 85 (P1-P85) separately in the right (RA) and left atria (LA). No sex differences were revealed at any age examined. VIP-LI has been already detected in both atria at P1 in concentrations comparable to values at P10. In the RA, VIP-LI levels increased significantly between days P10 and P25, remained high at P45 and then declined. In the LA, VIP-LI concentrations did not differ from those in the RA on days P1, P10, P25, and P45. However, regional differences were found at P60 and P85, when the peptide levels were significantly higher in the LA than in the RA. The postnatal changes in CGRP-LI concentrations were comparable in both atria with similar values at P1 and P85. After birth, CGRP levels decreased gradually till P45, then they increased till P60 and declined again at P85. The results demonstrate that there is an asymmetry in the postnatal development of the atrial VIP-LI and CGRP-LI concentrations. VIP-LI levels reached their maximum at P25, whereas CGRP-LI levels at P60. Relatively high peptide concentrations in neonatal atria and their variations during development might be related to diverse trophic functions of VIP and CGRP.

CGRP innervation and receptors during aging of male and female hepatic rat portal veins

Calcitonin gene-related peptide (CGRP) innervation and binding sites were studied on hepatic portal veins of male and female rats from 19 days to 22 months of age. CGRP containing nerve fibers were present both in adventitial and medial nerve plexuses, closely apposing to or penetrating into the muscular layers. The density of CGRP innervation was estimated on whole mount preparations and compared during aging. In females, aging did not affect the number of fibers per unit length, although the vessel circumference decreased after 6 months of age. In males, the vessel circumference remained constant during aging, while the density of innervation significantly decreased. Whatever the age or sex of the animals was, no CGRP binding sites were found on portal veins sections by autoradiography. CGRP had no effect on spontaneous contractions of perfused portal veins. The difference observed in the evolution of CGRP innervation density between males and females suggests that CGRP innervation in the rat portal vein may be influenced by gonadal steroids during aging.

Cytoskeletal features in longitudinal and circular smooth muscles during development of the rat portal vein

Immunohistochemistry of alpha-smooth muscle actin and desmin, two markers of smooth muscle cell differentiation, and electron-microscopic observation of thick filaments of myosin were performed on the media of the developing rat hepatic portal vein to gain insights into the chronology of differentiation of its longitudinal and circular smooth muscles. In accordance with the ultrastructural distribution of thin filaments, staining of alpha-smooth muscle actin is lightly positive in the myoblasts at postnatal day 1 and then extends in probably all muscle cells of the developing vessel. Desmin, which appears later than alpha-smooth muscle actin in the two muscles, is distributed throughout the longitudinal layer at day 8, whereas the first arrangements of thick filaments are detectable in most longitudinal muscle cells; at this stage, desmin and thick filaments are absent from the poorly differentiated circular muscle cells. The longitudinal muscle cells differentiate in a strikingly synchronized way from day 8 onwards, conferring a homogeneous structure to the developing and mature longitudinal layer. Several desmin-positive cells and a heterogeneous distribution of thick filaments occur in the circular muscle at day 14; the subsequent extension of these filaments in this layer results in a persisting heterogeneous distribution in the young 7-week-old adult. Many features of the mature smooth muscle cells are established within the third week in the longitudinal muscle, approximately one week before those of the circular layer. These results are consistent with the function of the longitudinal muscle as a spontaneously contractile smooth muscle unit, and emphasize the need for its fast maturation to fulfil its major role in the control of portal blood flow.

Calcitonin gene-related peptide innervation and binding sites in rat aorta during development

Indirect immunohistochemistry performed on whole mounts of arch and thoracic part of the rat aorta at six developmental stages (from embryonic day 17 to 6 months, in males and females) revealed that calcitonin gene-related peptide (CGRP) innervation is highest in the arch. The highest density of innervation is found at the three first postnatal ages investigated (day 1, day 3 and 5 weeks; 2.6 +/- 0.6 intercepts/mm in the arch at 1 day); however, all values are low compared to other arteries. The innervation grows from a few short isolated fibres in the embryo to a more complex meshwork in older animals. No striking differences were noticed between males and females. Autoradiographic studies were performed on serial sections at several levels of the aorta but did not reveal binding sites for CGRP in the vascular wall. This might be due to the technique which does not allow visualization of low density of binding sites, or to binding sites of weak affinity. We discuss the possible importance of CGRP in rat aortic smooth muscle development.